Far-Ultraviolet and Visible Imaging of the Nucleus of M32
Casertano, Stefano; Cole, Andrew A.; Ballester, Gilda E.; Crisp, David; Grillmair, Carl J.; Holtzman, Jon A.; Trauger, John T.; Gallagher, John S., III; Hester, J. Jeff; Mould, Jeremy R.; Hoessel, John G.; Clarke, John T.; Stapelfeldt, Karl R.; Burrows, Christopher J.; Griffiths, Richard E.; Scowen, Paul A.; Watson, Alan M.; Westphal, James R.
United States, Australia
Abstract
We have imaged the nucleus of M32 at 1600 Å (FUV) and 5500 Å (V) using the Wide-Field/Planetary Camera 2 (WFPC2) aboard the Hubble Space Telescope. We detected the nucleus at 1600 Å using the redleak-free Woods filter on WFPC2. The far-ultraviolet (FUV) light profile can be fitted with a Gaussian of FWHM 0.46" (4.6 pixels) but cannot be resolved into individual stars; no UV-bright nuclear structure was detected. The (FUV - V) color of the nucleus is 4.9 +/- 0.3, which is consistent with earlier observations. We are unable to confirm any radial variation in (FUV - V) within 0.8" of the nucleus; beyond that radius the FUV surface brightness drops below our detection threshold. We also performed surface photometry in V and found our results to be in excellent agreement with deconvolved WFPC1 results. M32's light profile continues to rise in a nuclear cusp even within 0.1" of its center. No intermediate-age stellar population is required by evolutionary population synthesis models to reproduce the (FUV - V) color of the nucleus, although these data and current models are insufficient to resolve this issue.
Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.